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At least 721 records · Page 40Linked to original sources
PubMed2004

A new species of salamander of the genus Hynobius from Central Honshu, Japan (Amphibia, Urodela).

We describe a small salamander from south Central Honshu, Japan, as a new species, Hynobius katoi. The genetic distances between this species and several named species, including sympatric H. kimurae, derived from allozyme data from a starch gel electrophoresis, proved to be sufficiently large to differentiate it at a specific rank. Distribution of this species is confined to the montane regions of Shizuoka and Nagano Prefectures, on the Akaishi Mountains of the Chubu District, central Japan. It is regarded as a member of the naevius group of Hynobius, characterized by small number of large, pigmentless ova. The species differs from the other species of the naevius group by the combination of relatively small body size, nearly spotless body, relatively few vomerine teeth forming moderately shallow series, and unique electrophoretic pattern of isozymes.

Animals↗
PubMed2005

Karyotype of a Japanese salamander Hynobius katoi and its implication on breeding ecology (Amphibia: Caudata).

Karyotype of a Japanese small salamander, Hynobius katoi, was first described. All individuals examined had 2n=58 chromosomes, consisting of nine pairs of biarmed macrochromosomes, four pairs of biarmed medium-sized chromosomes, six pairs of biarmed microchromosomes, and 10 pairs of uniarmed microchromosomes, although distinction of the second and the third groups of chromosome pairs was not clear. All pairs appeared homologous and no sexual dimorphism was found. Possession of 2n=58 chromosomes in H. katoi strongly suggests its lotic-breeding habits as was expected from the number and size of eggs and adult morphology. When compared morphology of chromosomes among lotic-breeders with 2n=58 chromosomes, metacentric nature of No. 10 seems to characterize the karyotype of H. katoi.

Animals↗
PubMed1989

The blood vascular architecture of the salamander external gill: a scanning electron microscopic study of corrosion casts.

The blood vascular architecture in three-paired external gills of salamander tadpoles, Hynobius dunni Tago, was demonstrated with special reference to metamorphosis by scanning electron microscopy of vascular corrosion casts. In the fully developed gill, each of the three-paired afferent branchial arteries gave off secondary afferent filament arterioles. The afferent filament arteriole drained toward the efferent filament arteriole, forming the loop at the posterior extremity of the gill filament. The branched capillaries from the afferent filament arteriole formed two plates of respiratory capillary networks with irregular honeycomb-shaped meshes. In addition, there were non-respiratory shunts as bypass of the blood circulation between the afferent and efferent branchial arteries without branching filament arterioles. Furthermore, the deep venous plexus and subepithelial capillary plexus were seen around each efferent branchial artery. The filament central venule in the central part of the filament merged into the venous plexus. Nutritive capillaries branched from efferent branchial arteries also drained toward the venous plexus. Such general vascular architecture is simpler than that of the fish. During metamorphosis, the pattern of the vascular distribution, especially filament net capillaries became irregular, and then markedly tortuous or convoluted blood vessels occurred in the absorbing gill. At the metamorphic climax, the capillary network practically disappeared in the remnant of the gill but the bypass shunt as a non-respiratory artery remained almost unchanged.

Animals↗
PubMed1995

Variations in the numbers of phalangeal bones in the four-toed salamander, Hynobius tenuis (Amphibia: Hynobiidae), from two localities in Toyama Prefecture, Central Japan.

Variations in the numbers of phalangeal bones in the fingers (I to IV) and toes (I to V) of specimens of Hynobius tenuis collected from two localities (Ashikuraji and Arimine) in Toyama Prefecture, Central Japan, were recorded. In the case of fingers of fore limbs, eight phalangeal formulas were distinguished, and in the case of toes of hind limbs, ten phalangeal formulas were recognized. In the fingers of specimens from Ashikuraji, the predominant formulas were 2-2-3-2 (40%) and 2-2-3-1 (32%). In specimens from Arimine, 2-2-3-2 was predominant (75%). In toes, the predominant formula was 2-2-3-2-0- (96%) for Ashikuraji and 71% for Arimine. The maximal number of phalangeal bones, 2-2-3-3-2, found in the toes of specimens from Arimine seems to represent the fundamental formula in hynobiid salamanders. The predominant formula, 2-2-3-2-0-, observed in the two populations may have been derived from the fundamental formula by degeneration of the phalangeal bones in the fourth and the fifth toes. The reason why phalangeal bones were degenerated in this species is discussed from an ecological viewpoint of body growth.

Animals↗
PubMed1975

Mycotic granuloma in a tiger salamander.

An unidentified brown-pigmented fungus was the cause of a granuloma in the left lumbar musculature of a captive female tiger salamander. Histologically, the fungus appeared in the granulomatous tissue both as round yeastlike budding cells and as long septate hyphae.

Animals↗
PubMed1999

Precocious testicular growth in metamorphosis-arrested larvae of a salamander Hynobius retardatus: role of thyroid-stimulating hormone.

Precocious maturation of testes occurs in goitrogen-treated larvae of a salamander Hynobius retardatus, a particular population of which has been reported to show a neotenic reproduction in a specific environment. Similar precocious growth of testes also was confirmed in thyroidectomized larvae in this study. A possible involvement of thyroid-stimulating hormone (TSH) in the precocious maturation of testes was examined in metamorphosis-arrested larvae whose thyroid or pituitary glands had been removed surgically at embryonic stages or which had been reared in goitrogens. The pituitary glands of both the thyroidectomized and goitrogen-treated larvae contained extraordinarily large number of TSH cells, which were called "thyroidectomy cells." When homogenates of the pituitary glands from the goitrogen-treated larvae were injected into the hypophysectomized larvae for a month, the testes grew larger than those in larvae injected with the pituitary glands from normally metamorphosed controls. These results are consistent with the idea that an extraordinarily high concentration of TSH, which is induced by either thyroidectomy or goitrogen-treatment, causes the precocious maturation of testes in the metamorphosis-arrested larvae of Hynobius retardatus. In contrast to the precocious testicular development, ovarian development in the metamorphosis-arrested larvae was almost identical to that in normally metamorphosed animals within our experimental period. This also suggests that in males the absence of thyroid hormones allows a gonadal response that in females may require another activator in addition to or following thyroid axis stimulation.

Animals↗
PubMed1999

Modulation of gelatinase activity correlates with the dedifferentiation profile of regenerating salamander limbs.

Remodeling of extracellular matrix (ECM) is one of the key events in many developmental processes. In the present study, a temporal profile of gelatinase activities in regenerating salamander limbs was examined zymographically. In addition, the effect of retinoic acid (RA) on these enzyme activities was examined to relate the pattern-duplicating effect of RA in limb regenerates with gelatinase activities. During regeneration, various types of gelatinase activities were detected, and these activities were at their maximum levels at the dedifferentiation stage. Upon treatment with chelating agents EDTA and 1,10-phenanthroline, the enzyme activities were inhibited indicating that those enzymes are likely matrix metalloproteinases (MMPs). Considering the molecular sizes and the decrease of molecular sizes by treatment with p-aminophenylmercuric acetate, an artificial activator of proMMP, some of the gelatinases expressed during limb regeneration are presumed to be MMP-2 and MMP-9. In RA-treated regenerates, overall gelatinase activities increased, especially the MMP-2-like gelatinase activity which increased markedly. These results suggest that MMP-2-like and MMP-9-like gelatinases play a role in ECM remodeling during regeneration, and that gelatinases are involved in the excessive dedifferentiation after RA treatment.

Ambystoma mexicanum↗
PubMed2000

GABA(C) receptors control adaptive changes in a glycinergic inhibitory pathway in salamander retina.

We studied the role of GABA in adaptive changes in a lateral inhibitory system in the tiger salamander retina. In dark-adapted retinal slice preparations picrotoxin caused a slow enhancement of glycine-mediated IPSCs in ganglion cells. The enhancement of glycinergic IPSCs developed slowly over the course of 5-20 min, even though picrotoxin blocked both GABA(A) and GABA(C) receptors within a few seconds. The slow enhancement of glycinergic IPSCs by picrotoxin was much weaker in light-adapted preparations. The slow enhancement of glycinergic inhibitory inputs was not produced by bicuculline, indicating that it involved GABA(C) receptors. The responses of ganglion cells to direct application of glycine were not enhanced by picrotoxin, indicating that the enhancement was not caused by an action on glycine receptors. In dark-adapted eyecup preparations picrotoxin caused a slow enhancement of glycinergic IPSPs and transient lateral inhibition produced by a rotating windmill pattern, similar to the effect of light adaptation. The results suggest that the glycinergic inhibitory inputs are modulated by an unknown substance whose synthesis and/or release is inhibited in dark-adapted retinas by GABA acting at GABA(C) receptors.

Adaptation, Ocular↗
PubMed2000

Somatostatin modulates voltage-gated K(+) and Ca(2+) currents in rod and cone photoreceptors of the salamander retina.

We investigated the cellular localization in the salamander retina of one of the somatostatin [or somatotropin release-inhibiting factor (SRIF)] receptors, sst(2A), and studied the modulatory action of SRIF on voltage-gated K(+) and Ca(2+) currents in rod and cone photoreceptors. SRIF immunostaining was observed in widely spaced amacrine cells, whose perikarya are at the border of the inner nuclear layer and inner plexiform layer. sst(2A) immunostaining was seen in the inner segments and terminals of rod and cone photoreceptors. Additional sst(2A) immunoreactivity was expressed by presumed bipolar and amacrine cells. SRIF, at concentrations of 100-500 nM, enhanced a delayed outwardly rectifying K(+) current (I(K)) in both rod and cone photoreceptors. SRIF action was blocked in cells pretreated with pertussis toxin (PTX) and was substantially reduced by intracellular GDP(beta)S. Voltage-gated L-type Ca(2+) currents in rods and cones were differently modulated by SRIF. SRIF reduced Ca(2+) current in rods by 33% but increased it in cones by 40%, on average. Both effects were mediated via G-protein activation and blocked by PTX. Ca(2+)-imaging experiments supported these results by showing that 500 nM SRIF reduced a K(+)-induced increase in intracellular Ca(2+) in rod photoreceptor terminals but increased it in those of cones. Our results suggest that SRIF may play a role in the regulation of glutamate transmitter release from photoreceptors via modulation of voltage-gated K(+) and Ca(2+) currents.

Ambystoma↗
PubMed2000

The ultrastructure of photoreceptor cells in the pineal organ of the blind cave salamander, Proteus anguinus (Amphibia, Urodela).

We studied ultrastructure of the photoreceptor cells in the pineal organ of blind, depigmented, neotenic cave salamander, Proteus anguinus. Unlike in epigean vertebrates the outer segments of most photoreceptor cells consists of concentrically arranged lamellae, however; in few cells, the outer segments contain 7-9 plasma membrane disks. In both types of photoreceptor cells the outer segments enclose lumps of vesicles of different sizes. The photoreceptor cells of Proteus anguinus are similar to those in other cavernicolous fish species.

Animals↗
PubMed2001

Temporal contrast adaptation in the input and output signals of salamander retinal ganglion cells.

We investigated how the light-evoked input and output signals of salamander retinal ganglion cells adapt to changes in temporal contrast, i.e., changes in the depth of the temporal fluctuations in the light intensity about the mean. Increasing the temporal contrast sped the kinetics and reduced the sensitivity of both the light-evoked input currents measured at the ganglion cell soma and the output spike trains of the cell. The decline in sensitivity of the input currents after an increase in contrast had two distinct kinetic components with fast (<2 sec) and slow (>10 sec) time constants. The recovery of sensitivity after a decrease in contrast was dominated by a single component with an intermediate (4-18 sec) time constant. Contrast adaptation differed for on and off cells, with both the kinetics and amplitude of the light-evoked currents of off cells adapting more strongly than those of on cells. Contrast adaptation in the input currents of a ganglion cell, however, was unable to account for the extent of adaptation in the output spike trains of the cell, indicating that mechanisms intrinsic to the ganglion cell contributed. Indeed, when fluctuating currents were injected into a ganglion cell, the sensitivity of spike generation decreased with increased current variance. Pharmacological experiments indicated that adaptation of spike generation to the current variance was attributable to properties of tetrodotoxin-sensitive Na(+) channels.

Action Potentials↗
PubMed2001

Temporal contrast adaptation in salamander bipolar cells.

This work investigates how the light responses of salamander bipolar cells adapt to changes in temporal contrast: changes in the depth of the temporal fluctuations in light intensity about the mean. Contrast affected the sensitivity of bipolar cells but not of photoreceptors or horizontal cells, suggesting that adaptation occurred in signal transfer from photoreceptors to bipolars. This suggestion was confirmed by recording from photoreceptor-bipolar pairs and observing a direct dependence of the gain of signal transfer on the contrast of the light input. After an increase in contrast, the onset of adaptation in the bipolar cell had a time constant of 1-2 sec, similar to a fast component of contrast adaptation in the light responses of retinal ganglion cells (Kim and Rieke, 2001). Contrast adaptation was mediated by processes in the dendrites of both on and off bipolars. The functional properties of adaptation differed for the two bipolar types, however, with contrast having a much more pronounced effect on the kinetics of the responses of off cells than on cells.

Adaptation, Ocular↗
PubMed2001

Differentiation behavior of pituitary cells in normal and metamorphosis-arrested larvae of the salamander Hynobius retardatus.

When premetamorphic larvae of the salamander Hynobius retardatus were treated with potent goitrogens, or subjected to thyroidectomy, their metamorphosis was completely arrested. The pituitary gland of the arrested larvae consisted mostly of the hypertrophied Thyroid Stimulating Hormone (TSH) cells that are called "thyroidectomy cells". The development and dynamics of the TSH cells were studied by investigating uptake of BrdU into pituitary cell nuclei and by double-staining immunohistochemistry using anti-pituitary specific antibodies. The majority of the BrdU-positive cells expressed the TSHbeta antigen, suggesting that TSH cells increased in number by their extensive proliferation in the pituitary glands of the goitrogen-treated larvae. On the other hand, double-staining immunohistochemistry showed that several prolactin (PRL) immunoreactive cells coexpressed TSHbeta within single cells even in normal controls. Furthermore, pituitary cells coexpressing PRL and TSHbeta increased in number in the goitrogen-treated larvae. Whereas cells coexpressing GH and TSHbeta were not observed in normal controls, they appeared in the pituitary glands of the goitrogen-treated larvae. These results provide morphological evidence for considerable phenotypic plasticity in the pituitary cells of H. retardatus.

Animals↗
PubMed2002

Effects of larval exposure to triphenyltin on the survival, growth, and behavior of larval and juvenile Ambystoma barbouri salamanders.

We exposed 10 sibships of the streamside salamander, Ambystoma barbouri, to two concentrations of triphenyltin (TPT) (1 and 5 microg/L) and an acetone carrier control for the entirety of the larval period. We measured effects on larval feeding rates, escape behavior, growth rates, and survival to, days to, and size at metamorphosis. Postmetamorphosis, we monitored feeding rates, growth rates, and survival of juvenile A. barbouri in order to investigate carryover effects. The 5-microg/L TPT concentration resulted in 93% mortality of the larvae. Exposure to 1 microg/L TPT had no mortality effect and no effect on the escape behavior of larvae. However, larvae exposed to this TPT concentration had significantly lower feeding rates and growth rates and therefore metamorphosed later than the controls but at the same mass. We detected a direct effect of TPT on growth rates beyond the effect through depressed feeding rates. We also found significant evidence for variation among sibships in their sensitivity to TPT toxicity. Once exposure was terminated at metamorphosis. we observed no residual effects of TPT on juveniles. Survival, feeding, and growth rates of juveniles exposed to TPT as larvae were not significantly different from those exposed only to the acetone carrier.

Ambystoma↗
PubMed2002

Biological activities of skin secretions of the salamander Tylototriton verrucosus.

Water-soluble skin secretions of salamander Tylototriton verrucosus, first described by Anderson in 1871, were studied for their biological and enzymatic activities. They were found to be toxic to mice with an intraperitoneal LD50 of 11.5 mg/kg. Using Sephadex G-75 gel filtration, it was proven that the toxic components of the secretions are proteins with molecular weights ranging from 30,000 to 50,000 Da. The secretions of T. verrucosus display a wide spectrum of antimicrobial activities and also contain both proteolytic activity and trypsin inhibitory activity. In contrast, neither hemolytic nor hemorrhagic activities were found. The secretions were determined to have phospholipase A2 activity; however, no acetylcholine esterase activity was detectable under the assay conditions.

Animals↗
PubMed1992

Retinal photoreceptor fine structure in the red-backed salamander (Plethodon cinereus).

The retinal photoreceptors of the red-backed salamander (Plethodon cinerus) have been studied by light and electron microscopy. Rods and single cones are present in this duplex retina in a ratio of about 25:1. The photoreceptors in this amphibian species are much larger than is reported for most vertebrates. In the light-adapted state, rods reach deep into the retinal epithelial (RPE) layer. The rod outer segment is composed of discs of uniform diameter displaying several very deep incisors. The rod inner segment displays a distal elliposid of mitochondria and a short stout myoid region. Rod nuclei are electron dense and often protrude through the external limiting membrane. Rod synaptic spherules are large and display several invaginated synaptic sites as well as superficial synapses. It is felt that the rods do not undergo retinomotor movements. The cone photoreceptors are much smaller than the rods and display a tapering outer segment, an unusual modified ellipsoid and a large parabolid of glycogen in the inner segment. Cone nuclei are less electron dense than rods and are located at all levels within the outer nuclear layer. The synaptic pedicle of the cones is larger, more electron lucent and display more synaptic sites (both invaginated and superficial) than that of rods. It is felt that cone photomechanical responses are minimal.

Animals↗
PubMed1992

Retinal pigment epithelial fine structure in the red-backed salamander (Plethodon cinereus).

The retinal pigment epithelium (RPE) of the red-backed salamander (Plethodon cinerus) consists of a single layer of large squamous shaped cells. The RPE cells are but minimally infolded basally (sclerally) but show many large apical (vitreal) processes interdigitating with the rod outer segments. These epithelial cells are joined laterally by prominent tight junctions located in the mid region of the cells. Internally smooth endoplasmic reticulum is very plentiful while rough endoplasmic reticulum is not. Polysomes, small dense mitochondria and small round to oval melanosomes are plentiful. Golgi zones and lysosome-like bodies are also present as are phagosomes of outer segment material and myeloid bodies. The RPE cell nucleus is large and vesicular. It is felt that the melanosomes undergo retinomotor movements but as only light-adapted specimens were examined it is not known how extensive are these movements. Bruch's membrane or complexus basalis shows the typical pentalaminate structure noted for most vertebrates. The choriocapillaris is a single layer of large anastomosing capillaries which are minimally fenestrated facing Bruch's membrane.

Animals↗
PubMed1992

Generalized linear models with random effects; salamander mating revisited.

In recent years much effort has been devoted to extending regression methodology to non-Gaussian data, where responses are not independent. These methods for dependent responses are suitable for data from longitudinal studies or nested designs. However, use of these methods for crossed designs seems to have serious limitations due to the intensive computations involved because of the intractable nature of the joint distribution. In this paper, we cast the problem in a Bayesian framework and use a Monte Carlo method, the Gibbs sampler, to avoid current computational limitations. The flexibility of this approach is illustrated by analyzing the interesting salamander mating data reported by McCullagh and Nelder (1989, Generalized Linear Models, 2nd edition, London: Chapman and Hall).

Analysis of Variance↗